T cell homeostasis and antitumor function require the Na+-K+-ATPase

The cancer-killing activity of T cells is often compromised within tumors, allowing disease progression. We previously found that intratumoral elevations in extracellular K+ constrain T cell antitumor function. Despite the relevance of K+abundance for T cell antitumor function and the importance of ion gradients for cellular physiology broadly, our understanding of T cell K+ transporters remains rudimentary7,8. Here, we report that the Na+-K+-ATPase is required for T cell quiescence, memory formation, and antitumor activity. Deletion of Atp1a1, the catalytic alpha subunit of the Na+-K+-ATPase, in CD8+ T cells induced constitutive activity in TCR, Akt-mTOR, and MAPK/ Erk signaling pathways. This state of tonic signal transduction was reflected in the acquisition of co-inhibitory surface receptors and terminal differentiation in T cells following Atp1a1 deletion. Mechanistically, we found that the Na+-K+-ATPase functions to support ROS homeostasis as its disruption produced ROS accumulation and the addition of antioxidants prevented the accelerated differentiation and acquisition of co-inhibitory receptors in T cells lacking Atp1a1. The in vivo behavior of T cells lacking Atp1a1 was also consistent with tonic signal transduction and stimulation-induced terminal differentiation. T cells lacking Atp1a1 could not achieve proliferative burst or form memory following pathogen challenge or perform tumor destruction in a syngeneic model of orthotopic murine melanoma. These results highlight the fundamental but underappreciated importance of monovalent ion transporters in T cell biology and have translational implications for the ongoing development of immune checkpoint blockade and T cell transfer therapies (i.e. CAR, TCR, TIL). Comparitive gene expression profiling of RNA-seq data for C57BL/6 murine CD8+ T cells electroporated with CRISPR-Cas9 molecules complexed to sgRNAs encoding Atp1a1 specific or scramble sequences